September 28, 2023

AMA #11: Improve Task Switching & Productivity and Reduce Brain Fog

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In the full AMA episode, we discuss:

  • What Can I Do in Order to Avoid Getting Brain Fog?
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ANDREW HUBERMAN: Welcome to the Huberman Lab podcast, where we discuss science and science-based tools for everyday life.


I'm Andrew Huberman, and I'm a professor of neurobiology and ophthalmology at Stanford School of Medicine. Today is an Ask Me Anything episode, or AMA.

This is part of our premium subscriber channel. Our premium subscriber channel was started in order to provide support for the standard Huberman Lab podcast, which comes out every Monday and is available at zero cost to everybody on all standard feeds-- YouTube, Apple, Spotify, and elsewhere. We also started the premium channel as a way to generate support for exciting research being done at Stanford and elsewhere-- research on human beings that leads to important discoveries that assist mental health, physical health, and performance.

I'm also pleased to inform you that for every dollar the Huberman Lab premium channel generates for research studies, the Tiny Foundation has agreed to match that amount, so now, we are able to double the total amount of funding given to studies of mental health, physical health, and human performance. So without further ado, let's get to answering your questions.

The first question is about task switching. And the specific question is, is there a way to get better at task switching? Well, task switching is an incredibly interesting topic. It's something that plagues many people. That is, a lot of people have challenges with task switching.

It's also a topic that people will often confuse with cognitive flexibility. So all of us-- well, unless it's been removed-- have an area of our brain called the prefrontal cortex. The words, "prefrontal cortex," actually refers to fairly varied real estate within the human brain.

So it's not one area of the human brain. Prefrontal cortex actually includes a lot of different subdivisions that do different things in the context of cognition and directing action, withholding action, these kinds of things. But one of the main functions of the prefrontal cortex is that when it's working well, it allows us to direct our focus and our cognition, our thinking, in a context-dependent way.

So one of the simplest ways to describe this is that when you took math in high school or if you're still taking math, your brain had to carry out certain types of cognitive operations that were very different than the types of cognitive operations that you need to carry out in your history class or your social studies class. But there were some features of all three of those classes that were the same, in the sense that presumably, you had to sit in a chair for all of those classes, you followed a certain set of rules that pertain to all three of those different classes, even though they're different subjects.

But then, there were certain rules that pertained just to mathematics, certain rules that you followed because the particular teacher was strict, not because of the topic they were covering, as well as certain rules that maybe you did not pay attention to, because a different teacher was a little more lax. For instance, maybe there was a teacher that let you put your feet up on the chair in front of you. Maybe another teacher forbid that at all costs.

The point being that your prefrontal cortex is the area of your brain that, along with other areas of your brain, ensures that you engage in context-specific behavior, context-specific thinking, and context-specific understanding about what you should and should not do. Now, cognitive flexibility is similar, in the sense that it describes your ability to switch the types of cognitive operations, as the name suggests, depending on what sorts of things you're trying to learn or understand.

And it's a lot more extensive than that. In fact, we will probably do an entire episode all about both cognitive flexibility, and perhaps even a separate episode on task switching. But task switching is somewhat distinct from cognitive flexibility. First of all, task switching requires cognitive flexibility, but they are not the same thing.

Now, when we talk about task switching, or rather, when you see task switching in the scientific literature, most often, it has to do with people performing one particular type of mental or physical operation. Say, they're maneuvering things with their hands or other parts of their body, or they are required to carry out one specific type of mental process, and then they are required, either at random intervals or at specific intervals, maybe every 10 minutes or so, to switch their attention and to do a different task entirely.

Now, in the laboratory experiment situation, this has most typically been carried out the following way. People are going to do one cognitive task, maybe mathematics, or they're going to count, for instance, from 1 up to infinity, as high as they can go in a given amount of time, in increments of, say, seven, or increments of 7 plus 1, then 7 minus 1. So these can be made increasingly difficult. You get the idea.

And then, perhaps a tone is played or they'll get a signal from the experimenter, and then they need to switch their task to doing something quite different, but also cognitive. That's the most typical arrangement. Or another typical arrangement in a task-switching experiment is that the person in the task-switching experiment will be asked to do some sort of physical manipulation of objects, maybe placement of puzzle pieces into the correct configuration.

Then, at some designated interval or intervals, they will have to switch to a different manual task. Fewer-- not zero, but fewer-- experiments have examined task switching between physical and cognitive tasks. OK? Now, there are these kind of outrageous examples that you can find on the internet.

By the way, I don't suggest that anyone go engage in these examples in real life of extreme task switching. One of the most notable ones would be chess-boxing. Believe it or not, this exists, where two people will enter a ring, and they will sit down at a table, and they will play chess for a given period of time.

So they're entirely focused on playing chess. Then a buzzer will go off. The chess table will be cleared, the chairs will be cleared, and they will be expected to box-- literally, fight for a round of, say, a minute to three minutes, and then go back to chess, then to boxing-- so-called chess-boxing.

Again, I'm not suggesting people chess-box. But I know that many people have challenges with task switching, and here, I can raise my hand and say that I am one such person. I've always had a pretty good ability to drop into deep focus, after a period of time, you know. I, like everybody else, takes a little bit of time to get into a book chapter or to get into a mode of physical exercise.

But once I'm doing something, I tend to be very, very focused on that, and I have a much greater challenge in switching out of that focused mode to doing the next thing, which is one of the reasons why oftentimes I run tardy. Because I'm still mentally thinking about or physically engaged in the thing that I was doing before. This is something I'm constantly working on.

And as a consequence, I've had to seek out and implement certain tools to improve my ability to task-switch. So I'm going to share a few of those tools with you now, because I know a number of people probably struggle with the same thing. And as I mentioned earlier, I'm also going to do a full-length episode about task switching, both the underlying mechanisms of task switching as well as a more extensive list of tools related to task switching as a full-length Huberman Lab podcast episode.

So how can we get better at task switching? Well, short of having somebody scruff you by the neck and force you to stop whatever activity you're doing and engage in the next activity that you're doing, one of the best things that we can do to support our ability to task switch that's nicely supported, both at the mechanistic level and at the practical level within the published literature, is to introduce short transition gaps between the activities that we're trying to switch between.

This is something that, in my opinion, has not been discussed enough. In fact, when was the last time you heard about the requirement for introducing gaps between tasks if you want to switch between them more efficiently? And yet, as a consequence of this not being discussed very often, I think a lot of people have placed an undue burden on themselves.

For instance, a lot of people think that when you sit down with a book and you're going to read, that you should be able to immediately focus on the material that you're reading and not have your mind flitting about. During the first 5, maybe even 10 minutes of reading a book chapter, unless you are absolutely enthralled from the first word or you are intensely curious what the material in that book chapter is-- maybe that book chapter is about you and what's going to happen to you next in your life, maybe the news article is about something that you care oh-so-much about.

But unless it's one of those specific instances, it's going to be about 5 or 10 minutes before the neural circuits in your brain that are required to understand and digest and commit that material to memory are going to come online at the levels of activity that are going to be required for you to experience that as intense focus, or even as mild focus. Because the activity of the brain is always going to be in a push-pull. This is extremely important for understanding task switching.

When you go from one task-- and maybe the task is simply to walk over to where the book is located-- to focusing on the material within that book, you have to both engage activity within certain neural circuits, and you need to disengage the activity of other neural circuits. Now, sometimes this is referred to as inhibition of certain neural circuits. Other times, it's just going to be a dissipation of activity of those neural circuits.

They're just going to quiet down, like a dimming of the lights in a particular room, while the activity of other neural circuits increases. OK? So the first thing that you really need to understand if you want to get better at task switching is that you cannot and you should not expect yourself to immediately drop into a narrow trench of focus or a narrow trench of ability for anything that you're not already extremely skilled at or extremely interested in knowing. OK?

One of the reasons why this is often overlooked is that, for instance, if we receive a text message from somebody and we are very interested in what's contained in that text message, maybe even eagerly anticipating the dot-dot-dot in that little window where the text message is going to arrive, like here it comes, here it comes, here it comes, it's an example of where you are able to immediately pay attention and absorb information. For instance, if you're trying to meet somebody in a big city and you need to know exactly where to meet them and you've arrived at the place where you thought you need to be, and then you can't find them, and you're waiting, waiting-- where are you? Where are you?

And you know, you're going to commit that information to memory, and you're going to act on it. But when you sit down to read a book of unknown content, or where you have just a general sense of what the content is, or when you sit down to do something like work on a spreadsheet or your taxes or engage in a conversation with somebody, expect a 5- to 10-minute transition period. I can't emphasize this enough, because I think a lot of people mistakenly think that they have issues with attention, and perhaps indeed, they have clinically diagnosable attention deficit hyperactivity disorder or some other form of attention deficit disorder.

Certainly can't rule that out based on this conversation alone. But a lot of people place this unfair burden on themselves to immediately be able to focus on a given task. And this is also true for physical tasks, right?

If you go to the gym to work out or you're heading out on a run or a cycling expedition, the idea that you would immediately be able to cycle at your peak performance or that you could perform sets and reps in the gym as best as you possibly could without any warmup, without any transition period-- that you could forget about the difficult or maybe even great conversation that you were having on the way in, or that you could forget about other activities that you need to do in the rest of your day-- I mean, that's just completely unfair, and it doesn't match at all the way that your neural circuits work. So you really need to match your expectation of your ability to focus on and perform a given task, whether or not it's cognitive or physical, to the actual underlying biology. OK? So that's the first point.

The second point is that we know that if you want to switch from one task to another task, that you are making it more difficult to drop into full task engagement, or rather, engagement with task B following task A, if you try and go immediately from task A to task B, that even the introduction-- I find this so cool-- even the introduction of an arbitrary but very short transition period of, say, 15 seconds, where you know that you're introducing 15 seconds of transition and you designate it as transition, will allow you to engage in a more efficient and more complete level of task execution on task B, if you introduce even a brief transition period.

Now, this, I find fascinating. Because what this means is that there are top-down influences. There are literally things that we can tell ourselves, based on an understanding of the underlying mechanisms, that allow us to task-switch better.

And this certainly doesn't involve taking any kind of prescription drug or supplement or doing anything differently, except as you go from task A to task B, knowing and designating that a transition period, even a very brief one, where you are not trying to perform task B, and that you've designated, this as a transition period-- I'm not trying to focus on the next thing that I need to do-- I might focus on it inadvertently, but I'm not deliberately trying to focus on it.

Rather, I'm going to think about what I just did and the fact that I'm no longer doing that, kind of leaving it like a fog behind, right? You're trying to move from this deep trench of attention, hopefully, on task A, or maybe you didn't achieve a deep trench of attention. And you're now done with task A, and you're not placing this unfair expectation on your neural circuits to just flip to task B.

And you're also acknowledging that task B is going to take 5 to 10 minutes to drop into fully. We already talked about that. But you're going to shorten that 5 to 10 minutes by deliberately introducing a transition period. And what comes in that transition period and its duration is important.

So first, let's deal with the duration. How long should the transition period be? Well, that is going to scale directly with how long you were in a deep trench of focus for task A.

But let's assume task A was something that was kind of light for you. Maybe you're just handling some email. Maybe you're talking to a coworker. Maybe you were at a board meeting and it was kind of light.

The stuff was just, OK, you're used to this stuff. This is the stuff that you do all the time. Now, you're headed back to your desk, or you're headed to your next class, or perhaps you did work out that morning, and now, you're going to head to your place of work.

Or maybe you're leaving work and you're going to engage with family. And you know you need to switch all these cognitive operations. You need to dump the stuff that you were just doing cognitively, and you now need to do a bunch of other things. Context is switching. Task is switching.

Well, just ask yourself, how deeply was I entrenched in that other activity? Was my mind flitting to other things? Or if I was in a deep trench of attention for that given thing, well, then you should give yourself slightly longer for this transition period-- maybe 5 or even 10 minutes, if you have that time. But even if you give yourself as short as 60 to 90 seconds of transition and you just designate it-- excuse me-- as transition, you're going to benefit in terms of your ability to do the next task.

So to be very clear, if you were in kind of a light task or something that didn't have much cognitive demand, well, then the transition period can be fairly short. It can be just a couple of minutes. Rather, if you were in a deep trench of attention, you really engaged in that first task, I suggest giving yourself a couple of minutes or more, maybe as much as 5 to 10 minutes. But you might not have that much time, in which case, give yourself any kind of transition, even if it's 10 seconds.

I certainly have had times in my life, in particular when I was a new assistant professor, meaning before I got tenure, where I remember sitting down to work on a grant, I'd get two lines out, and someone would knock on the door. Hey, where are the-- whatever-- the 30-mil syringes? Where do we keep the buffers? Or where's the-- we get this thing?

And OK, and then I'd have to shift my attention and go back to writing, and then I'd be distracted by something else again, which is not to say that people were distracting me unfairly. It was simply the case that at that time, my life required being involved in a lot more things than it did as my career progressed, at least in the short term.

So the point being that if you are deeply engaged in an activity, give yourself a little bit longer in the transition period between them. If you are sort of superficially involved in an activity, you need less of a transition period, but you need a transition period. What should come during that transition period?

Well, the most important thing to arrive in that transition period is a relative lack of attention to anything new. This is what's so destructive about the phone. And keep in mind, I am not one of these people that thinks that smartphones are terrible. In fact, I use mine, plural, very often, all day, often.

Not necessarily during deep cognitive focus, but in between those bouts of focus, I have to text-message people. I do work on there. I'm on social media. So certainly, not demonizing the smartphone.

However, if you finish a given activity, whether or not it's a cognitive or physical activity, and you are headed to something else that requires you do a new task, and that task requires significant amounts of attention and focus, well, then you would do very well to allow yourself a period of anywhere from 2 minutes to maybe as long as 10 minutes. I know this is going to be very hard for people, but 2 minutes to as long as 10 minutes, where you are not looking at your phone, you're not texting, you're not on social media, you're not foraging for anything.

In fact, you're trying to limit the total amount of information that you're bringing into your nervous system. Now, you don't have to walk around with eyes closed and try and not hear and not see. Let's be practical, folks. That's impossible to do anyway. You can't shut down your brain while awake.

You can go into states of deeper relaxation. There's non-sleep deep rest, which we'll talk about in a little bit. But you can't shut off your brain deliberately, OK? Not in any healthy way, that is.

But by introducing these transition zones or transition periods, as we'll call them, of 2 to 10 minutes between different tasks, and making sure that within those transition periods, you are not bringing in new information-- again, another context-- and what are you really doing? Well, you're ensuring that you're not going from task A to task B to task C. What we're talking about here is trying to limit your task switching between task A and task B and not introducing another task in between.

And you might think that looking at your phone is not a task, right? It's so easy. It's so reflexive. But it is. It's bringing in a lot of new context-- in particular, pictures and movies, which are a tremendous stimulus for the nervous system and anchoring your attention. It's bringing in new ideas, new thoughts that, no matter how hard you try, are going to intrude into your ability to perform task.

So when people say, how do I get better at task switching, I immediately want to say, please don't introduce yet more tasks. Switching from one task to another is hard enough already. Don't introduce another task in between.

Now, some of you might take this to mean that you shouldn't have a conversation with a coworker after a meeting while walking down the hall. I'm not saying that. I still encourage people to be social. I encourage people to engage in workplace environments.

However, I will say after many years of working in laboratories that at times were quite large-- you walk into the lab and there are a lot of different things going on-- one of the things that you learn how to do, if you're going to get good at your craft, is to not pay attention to what's going on with everyone crowded around a computer looking at who's winning at the World Cup. I'm not trying to insult soccer players here. I enjoy soccer, both playing it and observing it.

But one has to scruff themselves a little bit in trying to limit their attention to a number of different things in the environment and really go from task A to task B in a really dedicated way. Short lists benefit certain people. I know a lot of people are listmakers out there. They like to put two or three things, or maybe 20 things that they're going to accomplish each day.

One of the best tools that I ever learned, both for the sake of task switching but also for sake of just getting things done on a consistent basis-- I picked up while I was a master's student at Berkeley-- a very accomplished professor at that time told me that he writes down, every day, three things that he's going to accomplish and only three things, never more than three.

Now, he also included other activities. In fact, he was quite active in his physical life, so he rode his bike to campus. He also was a runner. He also went to the gym. He did not include those on his list of three things, but he would write down no more than three critical things to do each day.

So he had three critical tasks. So I've employed that method as well. I'll write down one, sometimes two, most often three, but if I can, just one or two tasks that I need to complete each day. And everything else is considered part of the, let's just say, automaticity function of my day-- things that I already know how to do that don't require a ton of cognitive focus.

But I limit the things that require a lot of cognitive focus to three things per day. However, those three things per day can take up many, many hours each, and certainly on the whole. OK, now, there are additional things that one can do to improve your ability to task-switch.

And one of the things that I found particularly beneficial is not a meditation, but rather is a perceptual exercise. And this is a perceptual exercise that I learned about when I was a graduate student, but in a totally different context. And it has to do with the way that your visual system and the parts of your brain that parse time are related to one another and influence one another.

Now, the reason this tool makes sense for improving your ability to task-switch is because it turns out that where you focus your visual attention strongly influences the way that your brain parses time. So I'll describe the tool first, and then I'll get a little bit into the underlying mechanisms. But again, I'll get deep into the underlying mechanisms as well as the tool-- as well as additional tools in a future episode about task switching on the Huberman Lab podcast.

So if you were to, for instance, close your eyes and not look at anything in your external environment, and just concentrate, for instance, on your breathing or the feeling on the surface of your skin-- I know this is starting to sound like meditation, but trust me, it's not meditation-- your perception of time-- that is, how finely you are slicing time-- would be distinctly different than if you were to open your eyes and focus on a faraway location-- say, way off in the horizon-- and not focus on your bodily sensations.

Similarly, if you were to focus your attention on some intermediate location, maybe, let's say, 20 feet away, and simultaneously focus on your internal bodily sensations or the surface of your skin, your perception of time, how quickly time was passing, would also be different than if you closed your eyes or if you were looking at some distant location. So the perceptual tool for task switching is a very simple one, and it's one that, frankly, I do every morning and have for many years now, and at least for me, has really enhanced my ability to task-switch.

And that is to just take a couple of minutes, and this really only takes about two or three minutes. And typically, what I will do is I'll start by closing my eyes. Oh, I should mention I typically do this in an environment where, ideally, I can see off into the distance, perhaps from a balcony if I'm in an apartment or a house, ideally outdoors. But if I'm indoors, I'll still do this. I'll just look as far off into the distance as I can when that step is required.

But I start off by closing my eyes and, essentially, not looking at anything, but directing my brain's focus to either the surface of my body, just what it feels like, what it's in contact with or not in contact with, maybe my breathing. Then I'll open my eyes, and I will focus on some location on my body, but my bodily surface, like my hand, at some distance. And I'll focus my attention there, maybe for just 5 to 15 seconds.

I should mention that the first station, as I call them, where my eyes were closed and I was focusing on my bodily sensations-- I also just do that for about 5 to 15 seconds. And I don't count specifically. Just kind of, roughly, 5 to 15 seconds.

OK, so second station, you're looking at the surface of your hand. And if you like, you can also concentrate on your breathing. But typically, people would just focus on some specific location on their hand.

Then I'll typically lower my hand, then I'll look off into the distance, maybe 5 to 10 feet. Doesn't really matter. Focus my visual attention there. Try and hold that focus for 5 to 15 seconds.

Then I'll look further off in the distance, maybe further still off into the distance. Ultimately, what I try and do is look at a location as far off in the distance-- into the distance-- excuse me-- as I possibly can. And I'm also trying to pay attention to my breathing at the same time, just as a way of calibrating my location to the location that I'm looking at and how great that is.

Then, typically, I'll close my eyes and return my attention to my immediate environment and my breathing, just in the location I'm in. So the entire thing only takes about two minutes. Again, starting with eyes closed, focusing on self, 5 to 15 seconds, then eyes open, focusing on surface of one's body, that is focusing one's visual attention, 5 to 15 seconds, maybe 10 feet away, then maybe 50 away, if you're in the metric system, meters, folks, works just as well. These distances do not have to be precise-- and then, off to the horizon, and then back to one's immediate location by closing one's eyes.

Now, what is happening when one does this perceptual exercise? And again, it's a perceptual exercise. It's a visual perceptual exercise. Well, what's happening is you are shifting your visual focus, obviously.

But you're also shifting the way in which you fine-slice or thick-slice time. Now, your ability to recognize consciously, whether or not your thin-slicing or thick-slicing time, is much harder to get a grasp of than it is to get a grasp of, whether or not you're looking at your hand, or often in the distance. That's kind of obvious.

But what we know for sure is that as you shift your attention from your immediate environment, out to different designated locations in your environment, and your time perception shifts accordingly, you're essentially training your brain to shift visual focus and the way in which you process in the time domain. And this is important in the context of task-switching, because so much of task-switching is not just to understand, OK, I'm going from reading to running, or from running to reading, and the different types of operations that are required in one case versus the other, but also a shift in the neural circuits that underlie your perception of time.

And again, this is a topic that deserves a much more elaborate discussion. But so much of our ability to execute a task with high proficiency has to do with getting our thinking and our actions into the correct time domain. Now, when I say "time domain," I know a number of people can get confused, because time is time, right? People think, what do you mean by time domain?

Space domain makes sense. Here, I'm not talking about outer space. Whether or not you're looking in one location or another, close to your body or far away from your body or different domains of space-- but the time domain is a little trickier for most people to understand.

So just think of it this way. When you see a slow motion movie, what you're seeing is a movie that was shot at a high frame rate, many frames per second. OK? The typical smartphone shoots movies at about 60 frames per second, some older ones 30 frames per second, the slow-mo function on your smartphone is actually a high-frame-rate function.

You took the same movie, but you took it at a higher frame rate. So you've got a lot more images. Therefore, you can generate slow motion. So with your visual system, when you focus very close in to your body, or you're focused on bodily sensations in your immediate environment, you are fine-slicing in the time domain, more so than when you are looking further off in the distance.

Similarly, when you engage in one type of task, like a board meeting or a Zoom meeting or a conversation with friends, you are in a very different set of neural circuit functions than when you sit down to read or learn math or lift weights or go to therapy or go for a walk with your dog, for instance. Now, it should be clear why when you move from task A to task B, you want to, A, introduce a transition period.

It can be very brief. Maybe you don't even have time for the two-minute transition period. You just say, OK, I'm in a transition period between task A and task B. I'm moving from this thing to that thing. I just need, like, 10 seconds.

I'm going to recognize, I'm going to count down 10 to 1, or 1 up to 10. Doesn't matter. This is transition time. But this is not a time to look at my phone or to be in lots of different time domains.

Now, you might say, well, does that mean I shouldn't look at the horizon while I'm walking from my meeting back to my desk? No. No, no, no. That's not the way that your brain works. It doesn't anchor to things that just happen to be in your environment, unless they're of particular interest.

What I'm saying is set a transition period between tasks-- ideally, 2, maybe as long as 10 minutes. I'm also saying that when you switch between tasks, or when you initiate your first major task of the day, please expect, do expect, a period in which it's hard to get into the groove, so to speak.

And in addition to that, I recommend having some of practice-- and I described the practice that I've used for some period of time now, at least for me, to great success-- where you are deliberately shifting your visual attention between different locations close to you and far away, and you're doing that as a perceptual practice. Again, the whole thing only takes about two minutes, maybe three minutes.

And you don't even need to do it every day. I happen to do it every day, but I miss the occasional day here and there. And even if you were to do this perceptual practice once a week or three times a week, I'm certain that you'll benefit.

Because in doing that perceptual practice, there's also an immediate recognition of the sorts of shifts that your brain is required to engage in any time you move from task A to task B or from task B to task C. And you start to see and feel-- literally, see and feel-- the way that transition occurs, and that it takes a little bit of time, but that you can accelerate that transition, if you understand that, oh, when I'm looking here and engaging in this type of behavior or sets of tasks, and then I'm now going to be expected to do another task in a completely different type of environment, that the brain is going to be required to shift over the neural circuits that are active and less active in order to do that, but that you can accelerate that process by practicing it, using that perceptual tool that I described.

So there, I covered some specific tools that one can use to enhance one's ability to task-switch, touching on a bit of the underlying neurobiology and why transition periods are useful, if not required. If you think about it, there's always a transition period when task switching. But here, you're taking conscious control over that transition period.

There are additional tools for enhancing one's ability to task-switch. They tend to be somewhat specific for the certain kinds of cognitive or physical tasks that one needs to do. The example of chess-boxing that I gave earlier-- a great example of task switching at its extreme, terrible example of a practice space-time bridging.

Very safe. I can't think of any way in which it might be dangerous, although please don't do it while driving or while operating any other machinery-- but by all accounts, very safe, zero cost, and we talked about some of the other tools for task switching as well.

Our next question is about brain fog. And the particular question is, what can I do in order to avoid getting brain fog? And what can I do when I have brain fog and I want to shut it off? OK, well, this is an excellent question, because a lot of people struggle with brain fog.

But we need to define what brain fog is, because there are a lot of reasons why one can feel like they might have brain fog. But we're going to be better off answering this question if we define what brain fog is from a bit of a physiological standpoint. And while there isn't one single operational definition for brain fog-- by the way, an operational definition is a definition that most or everyone in a given field agrees upon.

I think it's fair to say that when people talk about brain fog, they're talking about an inability to concentrate, and it's often accompanied by sleepiness, daytime sleepiness in particular. So we can define brain fog as a major challenge, because indeed, many people report having brain fog, and some people, in fact, suffer from chronic brain fog.

Whenever it is they try and focus on something for sake of learning or just focus their attention on even a conversation, their mind starts to drift. And it's important to point out that brain fog is distinct from the symptoms of ADHD, Attention Deficit Hyperactivity Disorder. And while, certainly, people who have ADHD can also suffer from brain fog, the two things, or rather their symptomology, is thought to be distinct.

We can quickly deal with the distinction between ADHD symptomology and brain fog by saying that the symptomology of ADHD most often-- not always, but most often-- is associated with elevated levels of arousal but difficulty guiding one's attention and keeping one's attention on a given task, especially tasks that one is not that excited about. Right? Keep this in mind-- people with ADHD can maintain high levels of attention, but typically, those high levels of attention are restricted to activities or topics that they are very interested in or excited about, but it's the other stuff that they really have challenges with.

Now, the typical presentation of brain fog is that it is not associated with high levels of arousal that are creating difficulties in maintaining attention. Rather, it's as if one is in a bit of a cloud, or fog, as the name implies, that has one feeling like they're being sort of pulled under, that their levels of arousal are actually very low or are diminishing when they try and focus. So somebody will sit down to read or write or learn something or pay attention to a conversation or a lecture, and it's as if they're being pulled under.

Their levels of autonomic arousal are going down. OK? So that's one of the key distinctions between ADHD and brain fog-- is with ADHD, elevated levels of autonomic arousal-- typically, not always-- and with brain fog-- typically, not always-- lower levels of autonomic arousal, or even downward-trending levels of autonomic arousal. And autonomic arousal is the way that we refer to levels of energy, but in more physiological terms. OK.

So the question was, what can one do to avoid getting brain fog, and what can one do to deal with brain fog to eliminate it when one has it? OK, so let's talk about what one can do to avoid getting brain fog. In answering a question like this, we have to first acknowledge that there are going to be direct ways of avoiding brain fog, and there are going to be indirect ways of avoiding brain fog. What do I mean by that? Direct ways of dealing with anything, biologically, psychologically, et cetera, means tapping into the very mechanisms that create the thing that you're trying to avoid. OK?

Indirect approaches are the things that set the landscape for or the opportunity to deal with something. So oftentimes, on the podcast, I will distinguish between factors that mediate a given process that are involved directly in a process, versus factors that modulate a process. And the example I always give is the same one I'll give you now, which is, if there were to be an alarm in the building that I happen to be podcasting from right now, my attention would shift. My level of alertness would shift.

But we don't say that building alarms actually mediate levels of attention and arousal. Rather, they can modulate levels of attention and arousal. The factors that mediate levels of attention and arousal are things like epinephrine, norepinephrine, the amount of activity in particular brain circuits, et cetera. And of course, we devote a lot of time and attention to talk about those mediating mechanisms on the Huberman Lab podcast.

OK. So if we want to talk about what can one do to avoid getting brain fog, we need to first think about modulating the indirect factors. And the big one here is going to be, avoid poor or insufficient amounts of sleep. OK, it's sort of a "duh."

And it's a "duh," because all of us are familiar with the feeling of having not been rested enough, or had a night's sleep that just was kind of a toss-and-turn night, or a night's sleep that follows a particularly stressful psychological event, where you go to sleep and you're asleep, but you're dealing with something, you're grappling-- you might even be going through these little micro arousals or wakings throughout the night, and you sort of know you are. You wake up in the morning, and you know that the state that you're in when you wake up is very different than the one you were in throughout the night, but you just don't feel rested.

You don't feel that deep sense of rest, that get-up-and-go that hopefully arrives within the minutes or at least hour after you wake up. OK, so you have to get a great night's sleep if you want to be able to pay attention and to avoid brain fog in your daily cognitive and physical activities-- indeed, all activities. So I've covered the topic of sleep on a good number of Huberman Lab podcasts.

And I'll refer you to just a few resources in our podcast site that can really help you improve the quality and duration of your sleep. These things, by the way, are all accessible at zero cost. There's the "Master Your Sleep" podcast episode that I did a couple of years ago that is still very popular.

Again, timestamps-- you can navigate to the tools, or you can hear about the science underlying the tools and the tools. There's the "Perfect Your Sleep" episode. There's the guest episode with sleep expert and neuroscientist Dr. Matthew Walker from UC Berkeley, who also wrote the fabulous book why we sleep. And there is a zero-cost toolkit for sleep that you can access by going to

Simply go to the Menu function, scroll down to Newsletter, and sign up for the newsletter by providing your email. By the way, we don't share your email with anybody. And you can also see previous newsletters in the form of PDFs right there, including the "Toolkit for Sleep."

"Toolkit for Sleep" and those other episodes describes the things that you should really do each and every day and night in order to ensure the best possible night's sleep. And I'll just highlight a few of those now, but really, the resources I just described are the place to go to get the full extent of the tools. The most important thing for getting a great night's sleep is going to be the thing I always talk about, which is to get sunlight in your eyes, or if you don't have access to sunlight, bright light in your eyes in the first hours after waking.

Ideally, as soon as you wake up, you get sunlight into your eyes. But depending on time of year location, et cetera, you might not be able to do that. But as soon as you possibly can get at least 10 to 15 minutes of sunlight in your eyes early in the day, and if you don't have access to sunlight for whatever reason, try and get some bright light in your eyes.

You don't necessarily have to purchase a daylight simulator. Those can be very expensive. But if you need to, you certainly can. We don't have any relationship to any SAD lights, as they're called, or any SAD light vendors.

You can also get a 900-lux LED light that you can purchase at fairly low cost online. Again, I have no relationship to any of those light sources, financially or otherwise. But those are good ways to get light in your eyes-- that is, bright light in your eyes-- if you don't have access to sunlight.

But-- and this is a very important point-- there is really no artificial source that compares to the quality and effect of getting sunlight in your eyes early in the day, especially within that first hour or two after waking, and doing that on a consistent basis. That's the key. Do it on a consistent basis.

And all the details of how to do that-- for instance, you don't want to wear sunglasses or do it through a windshield or through a window. It's fine to wear glasses, corrective lenses, that is, or eyeglasses. However, how long to do it, the importance of blinking to protect your eyes, all of that is included in the "Toolkit for Sleep" and the episodes of the Huberman Lab podcast I refer to.

So that's the biggie for getting a great night's sleep. The other biggie for getting a great night's sleep is to avoid drinking caffeine after 2 or 3 PM, and certainly within the eight hours, and ideally, within the 12 hours before bedtime. And I know, I know, I know that everybody says they can drink caffeine and then fall asleep without any trouble, but the architecture of that sleep is not going to be as good as it would be if you avoided caffeine in the eight, and ideally, 10 or 12 hours before you go to sleep.

So you want to avoid that caffeine as you're heading into the second half of your day, certainly, and maybe even a little bit earlier. And the third thing, which is really a biggie for getting the best possible night's sleep, is to avoid bright-light exposure between the hours of 10:00 PM and 4:00 AM. If you wake up in the middle of the night and you need to go to the restroom or something, try and use dim lights.

Try and especially avoid overhead, bright lights. If you absolutely have to look at your phone in the middle of the night, really dim it down or get rid of all the blue light. There's a feature that allows you to do that and that I'll talk about in an Instagram post coming up soon.

But basically, you want to avoid bright-light exposure to your eyes as the nighttime is approaching. And of course, for reasons related to parties and going out, for reasons related to medical emergencies, or things that you have to do between the hours of 10:00 PM and 4:00 AM, there will be nights when you view bright light between 10:00 PM and 4:00 AM.

I hope that's for good reasons, not bad or emergency reasons. But don't obsess over the fact that you looked at a little bit of bright light in the middle of the night or you had a night out. That's not the point here.

The point is that you want to be as consistent as possible about the bright-light exposure early in the day, about avoiding caffeine within 8, 10, maybe even 12 hours prior to bedtime, and avoiding bright-light exposure to your eyes between the hours of 10:00 PM and 4:00 AM on most nights. You have to live your life. These things aren't possible to do all the time.

But those are the biggies. And then, the rest of the items, which are also biggies but I don't have time to go into in depth here, are contained within the resources that I talked about earlier. OK, so the reason I went on this riff about sleep and the importance of getting sleep is that if you are not sleeping well, you can't really say you have brain fog per se.

Most likely, what's happening is that there are indirect reasons related to the known effects of sleep deprivation on cognition and focus and attention that are causing excessive daytime sleepiness and what you're referring to as brain fog. But it is an indirect modulatory-- in this case, negative-- force on your ability to concentrate. It's creating brain fog.

So put quite simply, the big one for avoiding getting brain fog is going to be to make sure that you're getting the best possible night's sleep on a consistent basis. Now, with that said, there are some biological mechanisms-- in particular, neural circuit and neurochemical-based mechanisms-- that are associated with brain fog. So these are things like diminished levels of the so-called catecholamines, dopamine, norepinephrine, and epinephrine, which are released both in the brain and body, that when are present at diminished levels, that levels are too low, you're going to experience something like brain fog.

And that's because of the role of these catecholamines in both arousal and in attention, as well as learning, for that matter. Now, there are a variety of things that you can do to increase the catecholamines and offset brain fog. And these span the typical array of options when thinking about how to tap into your biology, or for that matter, your psychology in any way.

There are behavioral tools, meaning do's as well as don'ts. There are nutritional tools, including do's and don'ts. There are supplement-based tools, and of course, there are pharmaceutical-based tools, prescription drugs. So as far as behavioral tools go, we can divide it into two actionable categories.

The first is going to be intense effort, in particular, exercise effort. So we know that intense exercise, in particular, exercise that takes place over a fairly short duration of time-- so as little as five minutes, but extending out to about 45 minutes-- is going to increase the catecholamines, dopamine, norepinephrine, and epinephrine quite considerably, and leads to a fairly long-lasting increase in alertness and attention. Now, the typical forms of intense exercise that people employ when they're trying to increase catecholamines, and in doing so, also feelings of well-being, but at least in part to increase their levels of attention, that sort of feeling of feeling good all day, or I felt better after I trained.

High-intensity exercise pertains to resistance training. So this can be done with bodyweight machines or free weights or some combination of those. It could also refer to sprint intervals. And we did an entire series on different forms of exercise with Dr. Andy Galpin. You can find that also at

We also have a toolkit in the toolkit newsletter that I mentioned a bit earlier that details the exercise regimen that I follow, that includes both intense training as well as longer-distance-- let's just call it low-intensity training, cardiovascular training and so forth. So if you want details on how to do this type of training, you can find that there, again, at completely zero cost.

But intense exercise is going to be exercise where you're really taxing your cardiovascular and/or musculoskeletal system. So in the context of resistance training, this could take the form of circuit training, but more typically, it's going to take the form of sets and repetitions of resistance exercise, where you're pushing either to failure-- that is, an inability to move the weight or your body for another repetition in good form-- or close to that.

And as a consequence, you're going to be quite out of breath, at least at the end of those sets, or for cardiovascular-type training, it's going to be more of the interval or high-intensity interval training, or simply high-intensity training, that are going to get your heart rate elevated to about 80% of maximum, or approximately 80% of maximum. It could be 75, could be 85, or even higher, 90. The sorts of exercise that you decide to employ, whether or not it's sprinting or cycling or rowing, is going to depend on what you can do safely, that is without injuring yourself.

I always say, whatever exercise you're doing, whether or not it's resistance training, or whether or not it's cardiovascular training, you need to pick movements that you can do at a given intensity without harming yourself, so that you can come back and do more exercise, ideally, the next day and the next day. OK, so this is why I don't say run. This is why I don't say cycle.

This is why I say, I like to run and lift weights as my form of exercise, but some people really don't like to or can't run. For me, the rower might be a good substitute, but I don't like cycling, at least not on a road bike, for reasons that are very particular to me, but you might love that. OK?

So we're not talking about the specific movements that one does. We're talking about elevating one's heart rate to about 80% of maximum-- maybe a bit more, maybe a bit less-- and doing that for a period of about 12 minutes, out to maybe even 45 minutes if you're talking about something like resistance training, in order to get those heart rate increases. Now, of course, resistance training isn't done specifically to elevate your heart rate. It's done more typically, I should say, to generate some sort of adaptation response of increased strength, increased hypertrophy, or some combination of those.

Now, in thinking about using exercise, either cardiovascular or resistance training to decrease brain fog, or even to increase levels of attention, it's very important to understand that when you do high-intensity interval training or high-intensity training of any kind with weights or just with your body while running, any category of high-intensity training, the total duration of that high-intensity training sets the stage for how you're going to feel afterwards, meaning in the minutes, but also hours afterwards.

And here's the important thing to remember. If you do high-intensity training, say, in the early morning hours-- this is when I prefer to do it if I can-- or sometime before noon, what many people will find is if they keep that high-intensity training rather brief, so anywhere from 12 to 45 minutes, maybe 50 minutes, maybe, maybe, maybe 60 minutes, if you're extremely well-rested from the night before, then typically, you will maintain higher levels of focus, and indeed, lower levels of brain fog throughout the entire day.

And then, of course, as evening approaches, it's natural to feel more sleepy. Hopefully, you're dimming the lights and you're getting a great night's sleep to recover from your exercise, and also rewire your brain according to all the things you were trying to learn that dance. Because keep in mind that you actually learn while you sleep. That is, you trigger learning while you're awake, but you actually rewire your brain connections while you sleep, or in another form of deep rest called non-sleep deep rest.

So the point here is that if those high-intensity training sessions are done before noon, let's say, so early in the day, and they are restricted in their total duration-- so let's set the restriction for the total duration, just for sake of discussion here, at about 50 to 55 minutes for resistance training, and at about 30 minutes for high-intensity cardiovascular training. Because frankly, I don't know many people who can maintain 45 or 60 minutes of high-intensity cardiovascular training and still call it high-intensity training.

And this has to do with the inverse relationship between intensity and duration, and the fact that when you do resistance training over the course of an hour, all of that resistance training can be very high-intensity, because you have rest intervals in between that are quite lengthy, where typically, your heart rate returns to baseline or at least close to baseline. OK, so the point here, or the very specific takeaway, is that if your high-intensity training is kept of short duration, it will tend to offset brain fog.

However, if your resistance training is of high-intensity and you're extending into the 75 minutes of high-intensity training, again, with resistance-- so body weights, machines, free weights, and so on-- or, for instance, you see people in the gym or you know people who will do a full 90 minutes or two hours of high intensity resistance training, well, oftentimes what that will do is that will reduce total oxygen uptake by the brain in the period that follows that high-intensity training.

And this is something I covered in a previous episode of the podcast. It's also something that came up in that discussion that I did on the series on exercise science and physiology with Dr. Andy Galpin. If you train very intensely early in the day, that's great. It can give you a terrific physical and cognitive lift throughout the day.

But if that training session is too long-- again, we're cutting the threshold at about an hour for resistance training and about 30 minutes for, again, high-intensity cardiovascular training-- for some individuals, maybe 45 minutes of high-intensity cardiovascular interval training that could get away with that, and then not have that brain fog and crash throughout the day. But most people, if they're training really hard early during the day and that extends too long, well, then they're going to experience brain fog later in the day.

So this behavioral suggestion is sort of a two-pronged suggestion. There's a do, and there's a don't. The don't is, don't train intensely for too long early in the day, and then expect your brain to function really well throughout the day.

And this is something that I don't believe is discussed nearly enough. Because we hear exercise is great for us, and indeed, it is. We hear that we need to do a combination of low-intensity and more moderate- and high-intensity exercise, which indeed is true. But what we don't hear is that if you do high-intensity training that's too long in duration, it's going to divert fuel-based resources, but more importantly, oxygen-based resources away from the brain and toward the body.

And anyone that's ever done a high-intensity 90-minute leg workout that included squats and/or deadlifts and a bunch of other movements, and did a lot of sets, and left the gym feeling like you left it all in the gym, knows what I'm talking about. So if you think about it, what I just described includes both a do and a do-not related to brain fog. And it's purely behavioral.

Now, there are some simpler-- and frankly, faster-- things that you can do using only behavior in order to offset brain fog by way of increasing the catecholamines. And the one that I come back to over and over again on the Huberman Lab podcast, not because it's trendy, not because I think that it's the be-all-end-all, and certainly not because I think it's a replacement for exercise or anything else, is deliberate cold exposure.

Deliberate cold exposure in the form of a cold shower or a plunge in a cold plunge of any kind with ice or just with cold water, or in a natural body of water where-- please be safe, by the way, folks. Never do any high-intensity breathing in combination with exposure to cold water. Please don't do that. People have been injured, and indeed, people have died doing that.

But just getting into cold water for 30 seconds to 2 minutes, maybe as long as 3 minutes if you're cold-water-adapted and you have some experience doing it-- if done safely, and there is a safe way to do this that I'll describe in a moment, is known to produce very fast and very long-lasting increases in the catecholamines-- in particular, norepinephrine and dopamine. And this is one of those behavioral tools where, at least if you're me, it does not feel good while you're doing it.

Frankly, a lot of times, it doesn't even feel good before you get into the cold shower or the cold bath, or the ice bath or the cold lake or the cold swimming pool. But afterwards, I and most people find that they feel much better, much more alert, both alert and calm-- elevated levels of attention, elevated motivation to focus on things that they want to learn and do throughout the day.

And so deliberate cold exposure is a very potent tool that is very distinct in its time course from high-intensity exercise. So it's something that you can do, and the range of costs for doing deliberate cold exposure is pretty enormous. Let's take the lowest level of cost. In fact, it's something that will save you money, and that's a cold shower.

If you are taking a cold shower as opposed to a hot shower, well, then you are going to offset the heating bill. And I'm somebody who likes to end with warm or hot water after a cold shower. Some people like to end with cold. Be my guest to do one or the other, depending on your preference.

People who are trying to increase their metabolism typically will end with cold. There's some debate as to how much deliberate cold exposure increases your metabolism. We're not talking about metabolism here. We're talking about increasing your level of catecholamines to offset brain fog.

Next up, the ladder on level of cost would be a ice bath where you're purchasing ice to put in the ice bath. Believe it or not, that can be fairly expensive. To get enough ice into an ice bath, that might cost you $40 or $50 in bags of ice, which, depending on your disposable income, may seem like a trivial amount or, I think, for most people, it's kind of a considerable amount.

So that's sort of the next level, but it's going to be a one-time thing. Once that ice melts, you can't use it, obviously. And you would have to purchase it again to do deliberate cold exposure.

The other approach, of course, would be if you have access to an ocean or a lake nearby. That can be zero cost, depending on what it costs to access that ocean or lake. And then, of course, there are commercial cold plunges. These are the ones that often get the most attention, and these are typically in the range of anywhere from $3,000 up to $25,000.

And that's where I think at least part of the criticism of deliberate cold exposure comes from. Oh, this is an attempt to just sell these fancy apparati of cold plunges. Keep in mind, you can always do the cold shower option. Is it as good as a cold plunge? Is it as good as an ice bath?

There are probably some minor differences. I think the consistency of doing the activity here is more important than the actual device that you use, whether or not it's a cold shower versus a cold plunge. And of course, then there's an even more expensive way to do all this, which is cryo, right? So there's a machine that can deliver very cold environment to you right up to the neck.

It is a much higher cost than an ice bath, but of course, unless you own one of these devices, which are very, very expensive, you have to pay each time you do it, typically. And so what I've just offered to you is an array of actually zero-cost to negative-cost-- can reduce your heating bill-- to fairly high-cost ways to do deliberate cold exposure.

Again, I just want to say that deliberate cold exposure is but one tool to increase catecholamines, but it is a very potent tool to do that. Will it completely offset brain fog? Will it cure your brain fog? Certainly not. But if you're somebody who has very severe and chronic brain fog, doing deliberate cold exposure ought to offset at least a portion of that brain fog.

That said, for some people that have extreme brain fog, even deliberate cold exposure, even resistance training done intensely, or cardiovascular training done intensely, is not going to be sufficient to offset that brain fog. Now, as I go toward different types of tools, not just behavioral tools that can offset brain fog, we have to keep in mind some of the things that might actually be promoting brain fog. And here, there are a few interesting surprises.

One of the surprises, at least to me, is a body of research focusing on how excessive levels of capsule-based probiotics can increase brain fog. I know this is debated, but I'd be remiss if I didn't at least share with you the idea that's out there that you can look into further, and that perhaps we'll do an entire episode about on the podcast in the future, if the literature on this fleshes out a bit more.

The point here is that probiotics, and prebiotics for that matter, are great. In particular, prebiotic fiber-- in particular, getting probiotics from the foods you eat-- low-sugar fermented foods being the best source of prebiotic fiber and probiotics-- so things like kimchi, things like sauerkraut, things like pickles-- provided that the kimchi, sauerkraut, and pickles are of the sort that need to be maintained in the refrigerator, and that they are low-sugar varieties.

There's also things like kefir, things like kombucha. Again, the low-sugar varieties, things that need to be maintained in the refrigerator, are going to be the one that contains these live active cultures that are going to promote the proliferation of the healthy gut microbiota. This is a topic that I covered previously on the Huberman Lab podcast, both in terms of the mechanisms and the tools associated with those mechanisms, entitled "Gut Health."

There's also an episode of the Huberman Lab podcast that I did with expert guest, my colleague at Stanford School of Medicine, Dr. Justin Sonnenburg, that tapped into some of these tools, and certainly, a lot of mechanisms as well. And in both episodes, we really highlighted the fact that one of the best ways to ensure a healthy gut microbiome-- and we now know that gut health is oh-so-important and the gut microbiome is one of the best ways to support gut health-- is through the regular, that is daily, consumption of low-sugar fermented foods of the sort that I just described. And there are a few others that you can learn about in those episodes.

So probiotics and prebiotics and prebiotic fiber in the form of low-sugar fermented foods and these other sources referred to in those episodes is extremely important and does not-- I really want to emphasize-- is not going to and does not contribute to brain fog. However, capsule-form probiotics, while they do have their place-- OK, I want to be very clear here-- they do have their place at helping to reestablish a healthy gut microbiome, especially after one has taken probiotics or when one is in a dysbiotic state, where they have a depleted microbiome-- this could be anything from chemotherapy, all the way to excessive travel and jet lag, or you're dealing with some other sort of immune insult in the form of a flu or infection of any kind-- there is a place for capsule probiotics.

However, most of the time, if people are ingesting those low-sugar fermented foods on a regular basis, and perhaps you're getting a little bit of extra probiotic or prebiotic from a supplement like Athletic Greens, AG1, and of course, there are other supplements out there that contain probiotics but at fairly low levels, right? These aren't very high levels of probiotics that are present in Greens drinks and things of that sort.

Or you're drinking kombucha, or you're drinking kefir, or both-- you're going to be in that safe range, where you're not going to create brain fog. However, there is this growing idea that when people take excessive levels of probiotics in capsule form, in supplementation form, that it actually can increase brain fog. Now, you might say, why would that be?

This is because the gut microbiome is involved in creating the chemical milieu and the very chemicals that are in the synthesis pathways for things like serotonin and for GABA-- that is, for neurotransmitters and neuromodulators that impact our level of attention and alertness. So again, I want to be very clear. I'm not saying that capsule probiotics are necessarily bad.

In fact, there are times when I will take a capsule probiotic to just really buffer my gut microbiome, if I've been taking antibiotics for whatever reason or I have been sick for whatever reason, and I'm trying to really replenish my gut microbiome or ensure that it stays in a healthy state. But most of the time, you want to avoid capsule probiotics, unless, of course, your physician recommends them to you.

So the most important person to be hearing the message that I'm giving right now is the person who is suffering from brain fog, who might already be taking high doses of probiotics or probiotics in capsule form on a regular basis. You might want to take a look at that. Definitely talk to your doctor before you add or remove anything from your nutrition or supplement regimen.

And of course, for most people, please, please, please do take your gut microbiome seriously. Reinforce that gut microbiome through the ingestion of whole foods that include fibrous foods-- I'm a big believer in that-- as well as low-sugar fermented foods. I'm also a big believer in that, based on the science that's been discussed on this podcast. And frankly, it's been discussed elsewhere fairly extensively as well.

And if you need to rely on supplementation to further buffer your gut microbiome, well, then a foundational nutritional supplement such as AG1-- and of course, there are others out there. AG1 just happens to be the one that I'm most familiar with, because I've been taking it for, gosh, nearly 12 years now. And it's one that I'm very familiar with, but of course, there are others out there.

And I really want to emphasize this-- there is certainly no reason why you need to supplement probiotics or prebiotics if you're being especially careful to get those from the types of foods that we talked about earlier. My other suggestion for people that suffer from brain fog is to at least consider the emerging literature on creatine. And when we hear the word creatine, most people think, oh, creatine, that's about building bigger muscles.

And indeed, if you take creatine-- and by the way, the most effective form of creatine also, fortunately, turns out to be the most cost-effective form of creatine, which is creatine monohydrate. And the typical dosage for creatine monohydrate is going to be 5 to 10 grams per day. You often hear 5 grams per day, but if you're a larger individual and you look at the research, what you realize is that the typical dosage in the research is going to be based on body weight.

So for me, I'm about 220 pounds, about 100 kilograms, so I take 10 grams of creatine monohydrate per day. If you weigh less than I do, maybe half as much as I do, then 5 grams should be sufficient. You could also just take 5 grams a day consistently, because there's a sort of a load-in phase that, in the old days, it was suggested that people take high doses, like 20 or 30 grams per day, and then back off to a lower dosage.

But we now know that you can simply take a low dosage of creatine monohydrate each day, and over time, you will load the creatine into your muscles, and some other tissues as well, that I'll talk about in a minute. And indeed, there is a benefit to your muscles, to your strength, and to your power output that is quite robust and supported in the literature. And that's because that creatine is going to draw additional water stores into the muscles. It's also going to contribute to some of the actual function of the muscle fibers themselves.

This was covered in the exercise science series with Dr. Andy Galpin, so you can learn all about the mechanisms there if you like. Now, creatine monohydrate, despite being an effective tool for increasing muscular size, has also been studied extensively-- in fact, has been studied far more extensively for its clinical roles-- in particular, its ability to increase creatine phosphate stores in the brain. And your brain, like your muscles, relies on multiple different fuel sources, depending on the activities that it's engaged in. --

The point here is that when you take 5 grams, or maybe 10 grams of creatine per day, you're going to increase the-- I don't want to say activity, but you're going to increase the opportunity for the creatine phosphate system in the brain to be active. All right? There's a much bigger conversation to be had there. I'm avoiding a lot of nuance right now for sake of time. I'll return to this at a later time.

But there is fairly good evidence now that creatine supplementation has a cognitive enhancing role. Now, this has been most extensively studied in the context of things that also challenge the cognitive system, so in the context of sleep deprivation. So for instance, creatine supplementation may be effective in offsetting some of the cognitive deficiencies associated with mild sleep deprivation.

Creatine supplementation may also be effective in offsetting some of the cognitive deficits associated with altitude-- or novel altitude, because some people are adapted to altitude. Creatine supplementation has now also been shown to offset some of the fatigue, both cognitive and physical fatigue, associated with infections-- in particular, viral infections that occurred even months earlier. So there was a recent study that got a lot of attention in the press that I'll just briefly mention and you can go check it out, which is entitled "The effects of six-month creatine supplementation on patient- and clinician-reported outcomes, and tissue creatine levels in patients with post-COVID-19 fatigue syndrome."

Post-COVID-19 fatigue syndrome is a syndrome where people feel, as the name suggests, a lot of mental and physical fatigue. And for some people, it's mild, and for some people, it is both very long-lasting and very severe. And this was a small study, I want to emphasize. This was a small study-- only 12 patients with post-COVID-19 fatigue syndrome, who took 4 grams of creatine monohydrate per day.

And the researchers were able to see that creatine stores increased, both in particular muscles as well as within particular brain areas. So this is called white matter brain areas. White matter is where the myelinated, the fatty ensheathed fibers of neurons that we call axons and the myelin that allows for high-speed transmission between neurons that governs, essentially, every function, cognitive, and physical-- the point being that in this study-- here, I'm quoting from the study, by the way-- "taking creatine for six months appears to improve tissue bioenergetics--" so basically, referring to the availability of creatinine in the muscle and brain-- "and to attenuate clinical features of post-COVID-19 fatigue syndrome."

So the creatine supplementation, by the way, compared to placebo, manifested in a significant improvement in levels of attention, levels of arousal, and kind of readiness to perform mental or physical work, this kind of thing. We will provide a link to this study so you can parse it in more detail. Again, it's a small study, but an intriguing one. And it makes a lot of sense, frankly, that creatine supplementation might offset some of this post-COVID-19 fatigue that some people experience.

Because there's already a fairly extensive literature on creatine supplementation increasing brain, creatine phosphate stores, and improving cognition. So I think that creatine is an interesting and, certainly, a fairly low-cost approach if one wants to think about adding supplementation as a way to offset or even combat brain fog. So as I mentioned earlier, there are behavioral, there are nutrition-based, and there are supplementation-based tools to offset brain fog.

I just talked about, mainly, behavioral, but also some supplementation-based approaches. I didn't talk too much about nutrition, although, keep in mind what I said earlier about low-sugar fermented foods if we're keeping a healthy gut microbiome. So I think everyone agrees that ideally, most people are consuming mostly minimally processed or non-processed foods, really trying to avoid highly processed foods.

But if we are thinking about offsetting brain fog, we have to also understand that any time you eat any food, even if it's the healthiest food in the world, whatever that means to you, but that probably means non-processed or minimally processed-- and that's true whether or not you're a vegan, or you're following the carnivore diet, or you're an omnivore like me. Well, if you consume very high volumes of any food, whether or not it's ribeye steaks or apples, you're going to divert a lot of blood to your gut, and you are probably going to feel a bit fatigued, including a bit mental-fatigued.

So people rather obsess about which foods are going to increase alertness. And we've talked before on the podcast about how certain foods contain more l-tyrosine, which is an amino acid precursor, to dopamine. We've talked about foods that contain choline, which is a precursor, ultimately, to acetylcholine, which is a neuromodulator associated with attention.

And one can come away from a discussion like that or from other discussions about the relationship between food neurotransmitters and the role of neurotransmitters and alertness in the brain, and think, oh, I should eat certain foods and I'll feel more alert. And while that is sort of true, it's equally, if not more, important to remember that if you eat a large volume of any food, no matter what amino acids it contains, you're going to feel fatigued afterwards, because of the fact that you're going to divert a lot of bodily resources to digesting that food and clearing that food from the gut.

So the point here is that whatever foods you eat, you have to be mindful of the fact that if you eat excessive volume of those foods, you are going to feel sleepy. You're going to have what a lot of people think of as brain fog. And this is not a trivial point, because I think a lot of people think, oh, you know, I wake up, I slept well, I have my coffee, then I have my workday, I maybe worked out early in the day, then I eat my lunch, and then I feel really sleepy, and I have brain fog in the afternoon.

These are often the people that are relying on caffeine later in the day, which, again, I don't suggest. And for these types of people-- and by the way, this represents billions of people on our planet-- there are a couple of recommendations I can point to that are often very effective, such as delaying your caffeine intake by about 90 to 120 minutes after waking-- which, by the way, folks, I never said everyone needs to do.

What I've said-- and I'll continue to say-- is that for people that struggle with a pronounced dip in energy in the afternoon, so-called afternoon crash, even though they're sleeping well at night, that delaying your caffeine intake to 90 to 120 minutes after waking can often offset the afternoon crash. OK? I never said everyone should delay their caffeine intake by 90 to 120 minutes after waking. However, a lot of people that delay their caffeine for 90 to 120 minutes after waking find they have much more sustained energy levels throughout the morning and throughout the day.

OK. So that's point number one. The second is that for people that eat a very large lunch, you're going to feel sleepy afterwards-- or I should say, most people will feel very sleepy. The one exception might be if you exercised hard early in the day, hopefully not too intensely for too long, per our earlier discussion, well, then you might require a fairly large meal, or at least a fairly calorie-dense meal.

But if you put a large volume of food in your gut, whatever the caloric density, whatever the foods happen to be, it is entirely expected that you will have brain fog or a dip in both mental and physical energy at some period of time after doing that. So keep the meal sizes, not necessarily small, but make sure that those meal sizes are not excessive.

Now, the last point I want to make about offsetting brain fog goes back to supplementation and a little bit into prescription drugs. There is a fairly large category of supplements that some people refer to as nootropics, a word that I absolutely despise, because it means smart drugs, and frankly, there is no circuit in the brain for being smart. There are circuits in the brain for different types of mental operations.

But these are things that have shown some ability, some effectiveness, in elevating levels of alertness-- things like Alpha-GPC, which essentially serves as a precursor to acetylcholine, or l-tyrosine, the amino acid precursor to dopamine. Now, it's been argued that supplements like Alpha-GPC and l-tyrosine are not efficiently converted into the neuromodulator targets that they are claimed to be-- so things like acetylcholine and dopamine.

However, there's a decent body of literature to at least show that Alpha-GPC, when taken at dosages of 3 to 600 milligrams, maybe even as high as 900 milligrams for people that tolerate it very well, or people that take anywhere from 500 to 1,500 milligrams-- OK? I'm saying milligrams of l-tyrosine-- experience elevated levels of alertness. And in some studies, you can find evidence for increased level of attention, combating mental fatigue, and even improved cognition, although the cognition one is really where the data are particularly lacking.

And this is where we have to separate increased levels of alertness and ability to maintain attention from actual increased cognition or ability to perform certain cognitive operations. OK? So that's why I don't like that word, nootropic, because it lumps all of those things together. Nonetheless, there is evidence that Alpha-GPC, l-tyrosine, taken alone or together, sometimes in combination with caffeine, can increase levels of attention and alertness that are favorable for offsetting brain fog.

However, I don't think people should rely exclusively on these tools. Nowadays, I also hear about people taking paracetamol and huperzine. Huperzine increases acetylcholine a bit more potently and through a different pathway than Alpha-GPC, and so on and so forth.

I know that as soon as we get into a discussion about this, the tendency is to think, oh, either he's-- meaning me-- is simply suggesting supplements to offset brain fog. And certainly, that's not the case. You need to pay attention to the behavioral tools, the nutrition tools, the sleep-based items that I talked about earlier, before even considering supplementation.

But I think there's also the kind of reflexive response that a different group of people have, where they think, oh, these are supplements that cure brain fog, and that's not true. They operate in a context of how well-rested you are, whether or not you're caffeinated or not, whether or not you are cognitively interested in the material that you're trying to learn, and so on and so forth. So that's important to remember.

Now, in terms of prescription drugs to offset brain fog, there is the entire category of prescription drugs that, frankly, are both used for the treatment of ADHD, as well as abused, mainly on college campuses, but by people in the tech industry, the finance industry-- frankly, all industries-- for elevating levels of attention and focus for long periods of time. These are drugs, such as Ritalin, Vyvanse, Adderall, and others.

Again, as I pointed out in the episode on ADHD, those drugs can be very effective for certain people, both young and old, in treating ADHD, clinically diagnosed ADHD. They are not for everybody, but they are effective for a good number of people. So we don't want to demonize them in every case, but they are not for everyone.

Here, we're talking about brain fog in particular. And in terms of the ability for that category of drugs to offset brain fog, they do have efficacy. But typically, when people are taking those drugs to offset brain fog, we're not talking about offsetting the symptoms of ADHD, and therefore, we are talking about either off-label or illegal use of those drugs, which is not something-- certainly, the illegal use of those drugs is not something that I condone.

Off-label use-- well, that's something that you need to discuss with your doctor. There is a category of prescription drug that is definitely worth noting in the context of this conversation about brain fog that has been explored-- that is, there are good research and clinical data for the ability of this drug, or category of drugs, rather, to increase levels of focus and attention as well as cognition, especially under conditions of sleep deprivation, and in some conditions, brain fog as well.

And these are the drugs most typically known as modafinil and armodafinil, sometimes also referred to as Provigil, and they go by other names as well. Modafinil, Provigil, has been shown over and over again to increase cognitive ability when people are sleep-deprived, and more and more physicians are also now prescribing it for treatment of brain fog. One thing about modafinil, Provigil, is that it tends to be very expensive, or at least it used to be, which is why armodafinil was created.

Armodafinil is a lower-cost version of modafinil. Some people will argue that it's not as effective as modafinil. The clinical literature argued that it is as effective as modafinil, despite its lower cost.

That's something that really needs to be sorted out between you and your prescribing physician. And I want to underline, highlight, and boldface "prescribing physician," because I am not a fan of, nor am I condoning, people taking modafinil or armodafinil for brain fog without working with a physician. In fact, any time you're going to take a prescription drug or remove a prescription drug from your regimen, or anytime you're going to add a supplement or remove a supplement from your regimen, it is advisable that you consult with a physician.

So I just told you about a wide range of tools for offsetting brain fog, maybe even for treating brain fog. Those were, make sure you get excellent sleep, OK? I know it's hard to do. It involves a number of different steps. We talked about those steps earlier and the resources for learning more about those steps.

Talked about doing high-intensity training, ideally early in the day, and making sure that the high-intensity training is not of duration that's too long, that then you divert fuel sources away from your brain and you have brain fog. We also talked about deliberate cold exposure and why it is effective in increasing alertness, and can potentially offset brain fog. We talked about it in its different forms and the cost of those different forms, including negative cost for a cold shower.

I keep coming back to deliberate cold exposure. And here, by the way, I should mention that we've also done a toolkit newsletter about deliberate cold exposure. Again, just go to, go to the Menu, scroll down to Newsletter, sign up for the newsletter, and you can access that deliberate cold exposure protocol-- again, all at zero cost to you.

And then, we also talked about maintaining a healthy gut microbiome as being essential, but not taking excessive levels of capsule probiotics, because that itself may increase brain fog. We also talked about supplements like Alpha-GPC, l-tyrosine, piracetam, which, again, are not going to be the ideal first approach to dealing with brain fog, but provided you're doing everything else that we talked about, may be a good secondary or tertiary approach if you're still experiencing some brain fog.

And we talked about some prescription drug approaches that are gaining popularity. Those were modafinil and armodafinil, often called Provigil and Nuvigil. And here, just like with supplements, I don't think that prescription drugs should be the first approach, but they do often have a place for certain people who are doing all the things correctly behaviorally, in terms of do's and don'ts. They're eating correctly. They're not overeating.

They're eating the right foods. They're doing their exercise, maybe even supplementing with the sorts of things we talked about a moment ago, and they're still experiencing brain fog. In those cases, one might consider the prescription drugs.

And then, forgive me, I forgot to mention just now in my list, but earlier , we also talked about the fairly limited amount of data, but the mechanistically logical data, about creatine and offsetting brain fog, and in some cases, offsetting mental and physical fatigue in post-COVID-19 syndrome.

I'd like to take this time to thank you for joining me for this Ask Me Anything episode. And I'd like to thank you for being a premium subscriber to the Huberman Lab podcast. I'd like to remind you that if I haven't answered your question already, that I will be doing these Ask Me Anythings every month. I will continue to sift through the questions that are on the Premium website, and I would encourage you to put additional questions there and to upvote questions that you'd like to see the answers to.

If any of the questions that I responded to today you didn't feel were thoroughly answered enough, then please add a new question there and point that out. I will read all the questions that are there, and I will strive to answer them as thoroughly, concisely, and clearly as possible. Again, you can put those at And as always, thank you for your interest in science.


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